Image captions now in EN, also few text edits committed

docs/cluster.svg

docs/description.md

docs/failover.svg

docs/sharding.svg

docs/source_images/cluster.svg

docs/source_images/cluster_ru.svg

docs/source_images/failover.svg

docs/source_images/failover_ru.svg

docs/source_images/sharding.svg

docs/source_images/sharding_ru.svg

docs/source_images/storage.svg

docs/source_images/storage_ru.svg

docs/storage.svg